Wireless communication method and apparatus for wireless local area network system

ABSTRACT

A wireless communication method and apparatus in a wireless local area network (WLAN) system are disclosed. A wireless communication method according to one embodiment may include generating a high-efficiency Wi-Fi (HEW) frame including at least one of an HEW-SIG-A field and an HEW-SIG-B field which include channel information for communications according to an Orthogonal Frequency-Division Multiple Access (OFDMA) mode, and transmitting the generated HEW frame to a reception apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/154,779, filed Jan. 21, 2021, which is a continuation of U.S.application Ser. No. 16/440,641, filed Jun. 13, 2019, now U.S. Pat. No.10,931,336, which is a continuation of U.S. application Ser. No.14/868,908, filed Sep. 29, 2015, now U.S. Pat. No. 10,367,549, whichclaims the benefit of Korean Patent Application Nos. 10-2014-0130829 and10-2015-0136305, filed Sep. 30, 2014 and Sep. 25, 2015, which are herebyincorporated by reference herein in their entirety.

TECHNICAL FIELD

Exemplary embodiments relate to a wireless communication technology fora wireless local area network system.

BACKGROUND ART

In a wireless local area network (WLAN) system, communications betweenan access point (AP) and a station are performed. The AP providesstations with communication services to in a service range.

A basic configuration block of a WLAN system defined in IEEE 802.11 is abasic service set (BSS). A BSS may include an independent BSS in whichuser terminals in the BSS perform direct communications with each other,an infrastructure BSS in which an AP is involved in communicationsbetween a user terminal and a user terminal inside or outside the BSS,and an extended service set which connects different BSSs to extend aservice area.

DISCLOSURE OF INVENTION Technical Solutions

A wireless communication method according to one embodiment may includegenerating a high-efficiency Wi-Fi (HEW) frame including at least one ofan HEW-SIG-A field and an HEW-SIG-B field which include channelinformation for communications according to an OrthogonalFrequency-Division Multiple Access (OFDMA) mode; and transmitting thegenerated HEW frame to at least one reception apparatus.

In the wireless communication method according to the embodiment, theHEW-SIG-A field may include at least one of bit information indicatingan OFDMA mode, bit information indicating a number of space-time streams(NSTS) of channels transmitted in the OFDMA mode, and bit informationindicating a coding mode of channels transmitted in the OFDMA mode.

In the wireless communication method according to the embodiment, theHEW-SIG-A field may include at least one of bit information indicatingan OFDMA mode, bit information indicating a multi-user multiple-inputmultiple-output (MU-MIMO) mode, and bit information indicating a channelto be demodulated by each reception apparatus.

In the wireless communication method according to the embodiment, theHEW-SIG-B field may include at least one of bit information indicating abandwidth used by each channel in the OFDMA mode, bit informationindicating a modulation and coding mode used by each channel in theOFDMA mode, bit information indicating a partial allocation identifier(AID) used by each channel in the OFDMA mode, bit information includingsubchannel allocation information in the OFDMA mode, and bit informationindicating an NSTS of channels transmitted in the OFDMA mode.

A wireless communication method according to another embodiment mayinclude receiving, from a transmission apparatus, an HEW frame includingat least one of an HEW-SIG-A field and an HEW-SIG-B field which includechannel information for communication according to an OFDMA mode; anddetermining a channel to be used for communications using the channelinformation included in at least one of the HEW-SIG-A field and theHEW-SIG-B field.

In the wireless communication method according to the other embodiment,the determining of the channel may determine, based on the channelinformation included in the HEW-SIG-A field, a channel through which theHEW-SIG-B field is transmitted.

A wireless communication apparatus according to one embodiment mayinclude a processor to generate an HEW frame including at least one ofan HEW-SIG-A field and an HEW-SIG-B field which include channelinformation for communications according to an OFDMA mode; and atransmitter to transmit the generated HEW frame to at least onereception apparatus.

A wireless communication apparatus according to another embodiment mayinclude a receiver to receive an HEW frame including at least one of anHEW-SIG-A field and an HEW-SIG-B field which include channel informationfor communications according to an OFDMA mode from a transmissionapparatus; and a processor to determine a channel to be used forcommunications using the channel information included in at least one ofthe HEW-SIG-A field and the HEW-SIG-B field.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationnetwork according to an embodiment.

FIG. 2 is a diagram illustrating a structure of a wireless communicationapparatus according to an embodiment.

FIGS. 3A and 3B are diagrams illustrating a structure of a transmitterof a wireless communication apparatus according to an embodiment.

FIG. 4 is a diagram illustrating a structure of a receiver of a wirelesscommunication apparatus according to an embodiment.

FIG. 5 is a diagram illustrating channel allocation according to abandwidth in IEEE 802.11a/g/n/ac according to an embodiment.

FIG. 6 is a diagram illustrating a transmission bandwidth when a channelis in a busy state by interference.

FIG. 7 illustrates a structure of a VHT PPDU of IEEE 802.11ac (VHT).

FIG. 8 illustrates a configuration of an IEEE 802.11ac VHT-SIG-A field.

FIG. 9 illustrates a structure of an IEEE 802.11ac VHT-SIG-B field.

FIG. 10 is a diagram illustrating an example of a channel configurationin an Orthogonal Frequency-Division Multiple Access (OFDMA) mode.

FIG. 11 is a diagram illustrating an example of an IEEE 802.11HEW-format PPDU to which OFDMA is applicable.

FIG. 12 is a diagram illustrating a process of transmitting HEW-SIG-Aaccording to an embodiment.

FIG. 13 is a diagram illustrating a process of receiving HEW-SIG-Aaccording to an embodiment.

FIG. 14 is a diagram illustrating a process of transmitting HEW-SIG-Baccording to an embodiment.

FIG. 15 is a diagram illustrating a process of receiving HEW-SIG-Baccording to an embodiment.

FIGS. 16 and 17 are diagrams illustrating examples of an HEW-SIG-Astructure according to a first embodiment.

FIG. 18 is a diagram illustrating an example of an HEW-SIG-B structurein a case where a channel is allocated adjacent subchannels in a 40-MHzbandwidth according to the first embodiment.

FIG. 19 is a diagram illustrating an example of an HEW-SIG-B structurein a case where a channel is allocated adjacent subchannels in an 80-MHzbandwidth according to the first embodiment.

FIG. 20 is a diagram illustrating an example of an HEW-SIG-B structurein a case where a channel is allocated subchannels not adjacent in a40-MHz bandwidth according to the first embodiment.

FIG. 21 is a diagram illustrating an example of an HEW-SIG-B structurein a case where a channel is allocated subchannels not adjacent in an80-MHz bandwidth according to the first embodiment.

FIG. 22 is a diagram illustrating an example of an HEW-SIG-B structurein a case where allocation is performed by subchannel orsubchannel/symbol in a 40-MHz bandwidth according to the firstembodiment.

FIGS. 23A and 23B are diagrams illustrating examples of dividing an80-MHz bandwidth into 10-MHz subchannels and symbols according to thefirst embodiment.

FIG. 24 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a second embodiment.

FIGS. 25 to 27 are diagrams illustrating examples of an HEW-SIG-Bstructure according to the second embodiment.

FIG. 28 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a third embodiment.

FIG. 29 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the third embodiment.

FIG. 30 is a diagram illustrating a transmission process in a case whereOFDMA and MU-MIMO are combined according to a fourth embodiment.

FIG. 31 is a diagram illustrating an example of an HEW-SIG-A structureaccording to the fourth embodiment.

FIG. 32 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the fourth embodiment.

FIG. 33 is a diagram illustrating a reception mode according to thefourth embodiment.

FIG. 34 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a fifth embodiment.

FIG. 35 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the fifth embodiment.

FIG. 36 is a flowchart illustrating operations of a wirelesscommunication method according to an embodiment.

FIG. 37 is a flowchart illustrating operations of a wirelesscommunication method according to another embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following specific structural and functional descriptions areprovided only to illustrate embodiments and are not construed aslimiting the scope of claims to the descriptions made in thisspecification. A person skilled in the art can make various changes andmodifications from these descriptions. In this specification, the term“one embodiment” or “embodiments” is provided to mean that particularfeatures, structures or characteristics described in connection with theembodiment or embodiments are included in at least one embodiment and isnot understood to refer to the same embodiment or embodiments.

The terms “first,” “second”, and the like may be used to distinguishdifferent elements but are not construed as limiting elements. Further,the terminology used herein is for the purpose of describing particularembodiments only and is not intended to limit the embodiments. As usedherein, the singular forms are intended to include the plural forms aswell, unless the context clearly indicates otherwise.

It will be further understood that the terms “include” and/or “have,”when used in this specification, specify the presence of statedfeatures, integers, steps, operations, elements, components orcombinations thereof, but do not preclude the presence or addition ofone or more other features, integers, steps, operations, elements,components, or combinations thereof.

Hereinafter, embodiments will be described in detail with reference tothe accompanying drawings. In the description with reference to theaccompanying drawings, like reference numerals denote like elements, anddescriptions thereof will be omitted.

FIG. 1 is a diagram illustrating an example of a wireless communicationnetwork according to an embodiment.

Referring to FIG. 1 , a network 110 may be connected to a plurality ofaccess points (APs) 120. Each of the APs 120 may communicate with aplurality of stations 130 in a basic service set (BSS). In anindependent BBS (IBBS), one station 135 may simultaneously communicatewith a plurality of stations 140.

FIG. 2 is a diagram illustrating a structure of a wireless communicationapparatus according to an embodiment. Referring to FIG. 2 , the wirelesscommunication apparatus 200 may include a processor 210, a memory 220, atransmitter 230, a receiver 240, and a radio frequency (RF) front end250. The wireless communication apparatus 200 may be a device capable ofrealizing the following embodiments, which may correspond to atransmission apparatus or reception apparatus described in thisspecification. According to one embodiment, the transmission apparatusmay be an AP, and the reception apparatus may be a station.

The processor 210 may implement a function, a process and/or a methodsuggested in the present invention. The processor 210 may conductcontrol to perform digital transmission and reception functionssupported in communication standards. These functions may includeprotocol layer convergence procedure (PLCP), physical medium dependent(PMD), associated layer management, and medium access control (MAC)layers and be implemented by various methods.

The processor 210 may include an application-specific integrated circuit(ASIC), another chipset, a logic circuit, a data processing apparatus,and/or a converter which mutually converts a baseband signal and awireless signal.

The memory 220 may be configured in a combination of logic, a circuit, acode, or the like, without being limited thereto. The memory 220 mayinclude a read-only memory (ROM), a random access memory (RAM), a flashmemory, a memory card, a storage medium and/or other storage devices.

The transmitter 230 may perform a wireless signal transmitting functionthrough coding, puncturing, interleaving, mapping, modulation, inversefast Fourier transform (IFTT), and spatial mapping processes, withoutbeing limited thereto.

The receiver 240 may perform a wireless signal receiving functionthrough fast Fourier transform (FFT), equalization, demapping,demodulation, deinterleaving, depuncturing, and decoding processes,without being limited thereto.

The RF front end 250 may convert a digital baseband signal received fromthe transmitter 230 into an analog RF signal and transmit the analog RFsignal through one or more antennas.

Further, the RF front end 250 may receive an analog RF signal from theoutside through antennas and convert the received analog RF signal intoa digital baseband signal. The RF front end 250 may transmit theconverted digital baseband signal to the receiver 240.

FIG. 3A and FIG. 3B are diagrams illustrating a structure of atransmitter of a wireless communication apparatus according to anembodiment. Referring to FIG. 3A, a spatial mapper 310 may receivesignals to be simultaneously transmitted to a plurality of stations. Aweight vector calculator 315 may calculate a weight vector (matrix) tobe applied to transport streams of stations using a multiple-inputmultiple-output (MIMO) channel and determine stations to which signalsare simultaneously transmitted.

The spatial mapper 310 may map each input signal on a weighting usinginformation on the calculated weight matrix. An inverse discrete Fouriertransformer (IDFT) performer 320 may perform IDFT on weighting-mappedinput signals. A guard interval inserter 325 may insert a guard interval(GI) to an IDFT-processed signal and perform windowing to insert awindow.

FIG. 3B is a diagram illustrating a process of generating a signal to betransmitted to a station. Referring to FIG. 3B, a scrambler 330 mayscramble data to be transmitted by a transmitter of a station. Anencoder parser 335 may separate scrambled data as many as a number ofencodes. A forward error correction (FEC) encoder 340 may perform FECencoding on the separated data as many as the number of encodes.

A stream parser 345 may separate the FEC-encoded data as many as anumber of streams. An interleaver 350 may perform interleaving on theseparated data as many as the number of streams. A constellation mapper355 may map the interleaved data using binary phase-shift keying (BPSK),quadrature phase-shift keying (QPSK), 160 quadrature amplitudemodulation (QAM), 128 QAM, 256 QAM, or the like.

A spatial time block code (STBC) performer 360 may perform STBC on thedata transmitted from the constellation mapper 355. A cyclic shift delay(CSD) performer 365 may perform CSD on the STBC-performed data. TheCSD-performed data may be transmitted to the spatial mapper 310 of FIG.3A.

FIG. 4 is a diagram illustrating a structure of a receiver of a wirelesscommunication apparatus according to an embodiment. Referring to FIG. 4, the receiver 400 of the wireless communication apparatus may performanalog-to-digital (AD) conversion on data passing through a wirelesschannel after passing through an RF communicator (not shown).

A GI remover 410 may perform carrier sensing, automatic gain control(AGC), timing synchronization, and frequency offset estimation on theconverted digital data and remove a GI.

A discrete Fourier transform (DFT) performer 415 may perform DFT on theGI-removed data. A channel estimator 420 may estimate a channel based ona long training field (LTF) of the DFT-processed data. An MIMO detector425 may demodulate the data based on a data field of the DFT-processeddata and a channel estimation result by the channel estimator 420.

A demapper 430 may convert the demodulated data into a soft value neededfor FEC decoding. A deinterleaver 435 may perform deinterleaving on thedata converted into the soft value, and a stream de-parser 440 mayseparate the deinterleaved data according to a number of FEC decoders445. An FEC decoder 445 may perform FEC decoding on the transmitteddata, and a decoder parser 450 may combine pieces of FEC-decoded data. Ade-scrambler 455 may de-scramble the transmitted data to reconstruct thedata.

FIG. 5 is a diagram illustrating channel allocation according to abandwidth in IEEE802.11a/g/n/ac according to an embodiment. Referring toFIG. 5 , IEEE802.11a/g/n/ac WLAN systems may use various bandwidths,such as 20 MHz, 40 MHz, 80 MHz and 160 MHz (80 MHz+80 MHz), and includea primary channel and secondary channels in 20-MHz channel units.

In the WLAN systems, wireless communication apparatuses verify whetherthe channels are in a busy state or idle state, and transmit data whenthe channels are idle. The wireless communication apparatuses performtransmission depending on whether the channels are in the busy state oridle state as in Table 1.

TABLE 1 Bandwidth Sec- Sec- Sec- Transmission (MHz) Primary ondary20ondary40 ondary80 bandwidth 20 busy — — — 0 20 idle — — — 20 40 busydon't care — — 0 40 idle busy 20 40 idle idle 40 80 busy don't caredon't care — 0 80 idle busy don't care — 20 80 idle idle busy — 40 80idle idle idle 80 160(80 + 80) busy don't care don't care don't care 0160(80 + 80) idle busy don't care don't care 20 160(80 + 80) idle idlebusy don't care 40 160(80 + 80) idle idle idle busy 80 160(80 + 80) idleidle idle idle 160

Table 1 illustrates transmission bandwidths depending on whether thechannels are in the busy state or idle state. As in Table 1, thewireless communication apparatuses may verify whether the channel are inthe busy state or idle state in order of primary, secondary20,secondary40, and secondary80 and by bandwidth to determine atransmission bandwidth. As illustrated in FIG. 5 , when any one of20-MHz channels belonging to secondary40 is in the busy state in an APor station supporting an 80-MHz bandwidth, a transmission bandwidth is40 MHz.

FIG. 6 is a diagram illustrating a transmission bandwidth when a channelis in the busy state by interference. In the channel allocation methodillustrated in FIG. 5 , when any one of channels in 20-MHz units amongsecondary channels becomes busy in a case of supporting a widebandwidth, such as 80 MHz or 160 MHz, all the secondary channels may notbe used. For example, when any one of channels in 20-MHz units ofsecondary80 becomes busy in an AP or station supporting a 160-MHzchannel, 80 MHz of secondary80 is not transmitted, and thus an AP orstation capable of using 140 MHz uses only 80 MHz, thereby allowingfrequency utilization efficiency to deteriorate.

To prevent deterioration in frequency efficiency, a transmissionapparatus may divide a frequency channel to simultaneously transmit datato a plurality of reception apparatuses. As illustrated in FIGS. 7 to 9and Table 2, although an IEEE 802.11ac very high throughput (VHT)structure supports multi-user (MU)-MIMO, all transmission physical layerconvergence procedure (PLCP) protocol data units (PPDUs) need to havethe same bandwidth and bandwidth allocation follows the mode illustratedin FIG. 5 and Table 1, which may result in unsatisfactory frequencyutilization efficiency.

FIG. 7 illustrates a structure of a VHT PPDU of IEEE 802.11ac (VHT). Apre-VHT modulated field is repeatedly transmitted by 20 MHz, and a VHTmodulated field may be transmitted via beamforming. A transmissionapparatus may transmit a transmission bandwidth, a transport stream, achannel coding scheme, a modulation and coding scheme (MCS), or the likeusing a signal field (L-SIG, VHT-SIG-A, VHT-SIG-B) so that a receptionapparatus demodulates a transmitted signal. FIG. 8 illustrates aconfiguration of an IEEE 802.11ac VHT-SIG-A field. Referring to FIG. 8 ,the VHT-SIG-A field is divided for a single user (SU) and a multi-user(MU).

FIG. 9 illustrates a structure of an IEEE 802.11ac VHT-SIG-B field.Referring to FIG. 9 , VHT-SIG-B is configured such that constituent bitsare repeated with an increase in bandwidth. Table 2 illustrates aconfiguration of the VHT-SIG-B field.

TABLE 2 VHT MU PPDU Allocation (bits) VHT SU PPDU Allocation (bits) 80MHz 80 MHz 160 (80 + 160 (80 + Field 20 MHz 40 MHz 80) MHz 20 MHz 40 MHz80) MHz VHT-SIG-B  B0-B15  B0-B16  B0-B18  B0-B16  B0-B18  B0-B20 Length(16) (17) (19) (17) (19) (21) VHT-MCS B16-B19 B17-B20 B19-B22 N/A N/AN/A  (4)  (4)  (4) Reserved N/A N/A N/A  B7-B19 B19-B20 B21-B22  (3) (2)  (2) Tail B20-B25 B21-B26 B23-B28 B20-B25 B21-B26 B23-B28  (6)  (6) (6)  (6)  (6)  (6) Total bits 26 27 29 26 27 29

FIG. 10 is a diagram illustrating an example of a channel configurationin an Orthogonal Frequency-Division Multiple Access (OFDMA) mode.

In order to increase frequency utilization efficiency in a WLAN system,for a plurality of reception apparatuses, a transmission apparatus maydivide a bandwidth into channels to transmit data. FIG. 10 illustratesan example of dividing an 80-MHz bandwidth into three channels includinga first channel, a second channel, and a third channel. A bandwidth (BW)is a frequency range used for a transmission apparatus to transmit data.A subchannel is a group of subcarriers, which represents a minimumallocation unit. A channel is a group of subchannels, which represents abasic unit transmitted to a particular reception apparatus. Adjacent orseparate subchannels may be allocated as channels. In FIG. 10 , abandwidth is 80 MHz, a subchannel as a minimum allocation unit is 5 MHz,and channels in 20-MHz units are configured for a reception apparatus,that is, three channels including a 20-MHz first channel, a 40-MHzsecond channel and a 20-MHz third channel are configured.

FIG. 11 is a diagram illustrating an example of an IEEE 802.11HEW-format PPDU to which OFDMA is applicable. Respective channels may betransmitted for different reception apparatuses and have differentspace-time streams, and thus may have different numbers of LTFs. Todemodulate channels having different LTFs, HEW-SIG-B may be positionednext to a first HEW-LTF. The reception apparatuses using the respectivechannels may acquire parameters needed for reception including numbersof LTFs through information of HEW-SIG-B next to the first LTF.

FIG. 12 is a diagram illustrating a process of transmitting HEW-SIG-Aaccording to an embodiment. Referring to FIG. 12 , HEW-SIG-A may betransmitted by 20 MHz, and all reception apparatuses may be controlledto receive the same signal.

An HEW-SIG-A generator 1210 may generate a sequence configured in acombination of bits constituting the HEW-SIG-A field. The generatedHEW-SIG-A sequence may be subjected to a channel encoder 1215 and aninterleaver 1220 and be modulated by a constellation mapper 1225, andthe modulated signal may be subjected to IDFT by an IDFT performer 1230.A CSD performer 1235 may perform CSD on the signal received from theIDFT performer 1230, and a GI inserter 1240 may insert a GI into thesignal and perform windowing on the signal to transmit the signal maythrough an RF communicator 1245.

FIG. 13 is a diagram illustrating a process of receiving HEW-SIG-Aaccording to an embodiment. Referring to FIG. 13 , an analog-to-digitalconverter (ADC) 1310 may convert a signal received through receivingantennas into a digital signal. A GI remover 1315 may remove a GI fromthe digital signal. A DFT performer 1320 may perform DFT on theGI-removed signal.

A channel estimator 1325 may perform channel estimation on theDFT-processed signal using an LTF and perform signal detection based ona channel estimation result. When there is a plurality of receivingantennas, the channel estimator 1325 may combine detected signals. Thedetected signal may be subjected to a deinterleaver 1330 and bechannel-decoded by a channel decoder 1335. A demodulator 1340 maydemodulate HEW-SIG-B and data using information included in theHEW-SIG-A sequence which is channel-decoded and demodulated.

FIG. 14 is a diagram illustrating a process of transmitting HEW-SIG-Baccording to an embodiment. Referring to FIG. 14 , an HEW-SIG-Bgenerator 1410 may generate an HEW-SIG-B sequence including differentpieces of information by channels. The generated HEW-SIG-B sequence maybe subjected to a channel encoder 1415 and an interleaver 1420 and bemodulated by a constellation mapper 1425. The modulated signal may besubjected to a CSD performer 1430 and be mapped on a beamforming matrixby a spatial mapper 1435. Each signal mapped on a beamforming matrix maybe mapped on a subchannel by a subchannel mapper 1440.

An IDFT performer 1445 may perform IDFT on the signal mapped on thesubchannel, and a GI inserter 1450 may insert a GI into theIDFT-processed signal and perform windowing on the signal. The signalwhich is GI-inserted and subjected to windowing may be transmitted by anRF communicator 1455.

FIG. 15 is a diagram illustrating a process of receiving HEW-SIG-Baccording to an embodiment. Referring to FIG. 15 , an ADC 1510 mayconvert a signal received through receiving antennas into a digitalsignal. A GI remover 1515 may remove a GI from the digital signal. A DFTperformer 1520 may perform DFT on the GI-removed signal. A subchanneldemapper 1525 may perform subchannel demapping on the DFT-processedsignal.

A channel estimator 1530 may perform channel estimation on thesubchannel demapping-processed signal using an LTF and perform signaldetection based on a channel estimation result. The detected signal maybe subjected to a deinterleaver 1535 and be channel-decoded by a channeldecoder 1540. A demodulator 1540 may demodulate data using informationincluded in HEW-SIG-B information which is channel-decoded anddemodulated.

Hereinafter, embodiments of configuring HEW-SIG-A and HEW-SIG-B toimprove frequency utilization efficiency will be described. Positionsand bits of elements constituting HEW-SIG-A and HEW-SIG-B illustrated inthe embodiments may vary, and reserved fields may include information onelements necessary for transmission and reception of data which is notstated in this specification.

First Embodiment

An illustrative bit configuration of HEW-SIG-A is described as follows.

In one example, bits included in HEW-SIG-A to support OFDMA areillustrated in Table 3 below.

TABLE 3 Illustrative Name number of bits Note OFDMA 1 Bit to indicateOFDMA 0: OFDMA, 1: SU, MU OFDMA NSTS 16 Number of space-time streams(NSTS) of channels simultaneously transmitted in OFDMA mode B6~B9: NSTSof first STA B10~13: NSTS of second STA B14~B17: NSTS of third STAB18~B21: NSTS of fourth STA OFDMA [0-3] coding 1 Coding modes ofchannels simultaneously transmitted in OFDMA mode OFDMA[0] coding:Coding mode of first channel OFDMA[1] coding: Coding mode of secondchannel OFDMA[2] coding: Coding mode of third channel OFDMA[3] coding:Coding mode of fourth channel

FIG. 16 illustrates an example of an HEW-SIG-A structure according to afirst embodiment, and FIG. 17 illustrates another example of anHEW-SIG-A structure according to the first embodiment. FIGS. 16 and 17illustrate numbers of bits necessary for each element, which may varydepending on embodiments. Bits indicating OFDMA of HEW-SIG-A may beallocated in random numbers to random positions according toconfigurations based on parameters necessary for transmission.

A reception apparatus needs allocation structure information on whichchannel is allocated to the reception apparatus in order to demodulate asignal transmitted in OFDMA. Referring to FIG. 9 , 54 bits may be usedin a 40-MHz band, and 117 bits may be used in an 80-MHz band. When it ispossible to transmit a channel by 20 MHz, data transmission is possiblewith up to two reception apparatuses in a 40-MHz bandwidth, and datatransmission is possible with up to four reception apparatuses in an80-MHz bandwidth.

Hereinafter, examples of an HEW-SIG-B structure according to the firstembodiment will be described.

<HEW-SIG-B Structure in a Case of a Channel of Adjacent Subchannels>

HEW-SIG-B may be transmitted using a bandwidth indicated by a bit of aBW field of HEW-SIG-A. A reception apparatus may estimate a channelbased on a first HEW-LTF of the BW field indicated in HEW-SIG-A anddemodulate HEW-SIG-B.

FIG. 18 illustrates an example of an HEW-SIG-B structure in a case wherea channel is allocated adjacent subchannels in a 40-MHz bandwidthaccording to the first embodiment. Referring to FIG. 18 , when partialassociation identifier (AID)[n] indicates a reception apparatus, thereception apparatus selects BW[n] and MCS[n]. When there is no partialAID indicating the reception apparatus, the reception apparatusterminates reception to save power. In a cyclic redundancy checking(CRC) field of the HEW-SIG-B structure, other elements needed for CRC ortransmission and reception may be added or reserved bits may beallocated. Illustrated is an example of an HEW-SIG-B structure in a casewhere a channel is allocated adjacent subchannels in an 80-MHzbandwidth.

Illustrative structures of a BW field, an MCS field, a partial AIDfield, and an OFDMA pattern are in Table 4. Table 4 illustrates anexample of an HEW-SIG-B structure according to the foregoingembodiments.

TABLE 4 Illustrative number of Name bits Note BW field 8 Bandwidth usedby each channel in OFDMA mode, using 2 bits for each channel Ex) 00: 20MHz 01: 40 MHz 10: 80 MHz 11: 160(80 + 80) MHz MCS field 16 Modulationand coding used by each channel in OFDMA mode, using 4 bits for eachchannel Ex) 0000: BPSK ½ 0001: QPSK ½ 0010: QPSK ¾ 0011: 16 QAM ½ 0100:16 QAM ¾ 0101: 64 QAM ⅔ 0110: 64 QAM ¾ 0111: 64 QAM ⅚ 1000: 256 QAM ¾1001: 256 QAM ⅚ Partial AID field 36 Partial AID used by each channel inOFDMA mode, using 9 bits for each channel (a reception apparatusverifies using partial AID whether a signal is transmitted to thereception apparatus to save power) Ex) Partial AID[0]: Partial AID offirst channel Partial AID[1]: Partial AID of second channel PartialAID[2]: Partial AID of third channel Partial AID[3]: Partial AID offourth channel

An HEW-SIG-B structure in a bandwidth of 80 MHz or greater may be easilyextended from relationships between FIGS. 18 and 19 . FIG. 19 is adiagram illustrating an example of an HEW-SIG-B structure in a casewhere a channel is allocated adjacent subchannels in an 80-MHz bandwidthaccording to the first embodiment.

A reception apparatus may verify whether a PPDU operates in OFDMA basedon bits of HEW-SIG-A indicating whether an OFDMA operation is performedand identify a space-time stream of each station from OFDMANSTS.Further, the reception apparatus may identify a coding mode of eachstation from OFDMA coding. For instance, an example of extractingreception parameters using HEW-SIG-A and HEW-SIG-B in the foregoingembodiments is illustrated in Table 5.

TABLE 5 Effective BW[0-3], OFDMA NSTS Effective OFDMA coding MCS[0-3],Partial OFDMA [0-3] [0-3] AID [0-3] 1: [4, 2, 0, 0]: [0, 1, 0, 1]:Transmitted with first OFDMA mode Transmitted with two Transmitted withtwo two channels, and thus channels channels, and thus first two bitsfor first two First channel uses four bits are valid (OFDMA NSTSchannels are valid STSs of 0 means no transmission) Second channel usestwo STSs 1: [2, 1, 1, 0]: [0, 1, 0, 1]: Transmitted with first OFDMAmode Transmitted with three Transmitted with three three channels, andchannels channels, and thus first three thus bits for first three bitsare valid channels are valid 1: [2, 1, 1, 2]: [0, 1, 0, 1]: Transmittedwith four OFDMA mode Transmitted with four Transmitted with fourchannels, and thus bits channels channels, and thus first four for fourchannels are bits are valid valid

<HEW-SIG-B Structure in a Case of a Channel of Subchannels not Adjacent>

When a channel is formed of adjacent subchannels as described above, aposition occupied by each channel in the entire bandwidth may be easilyverified by identifying a bandwidth used by the channel. However, when achannel is formed of subchannels not adjacent, there can be variouscombinations of subchannels constituting the channel, and thus areception apparatus needs to recognize possible combinations ofsubchannels in advance and it is necessary to indicate information onwhich combination is used in PPDU transmission through HEW-SIG-B. In thefollowing description, a subchannel has a bandwidth of 20 MHz, withoutbeing limited thereto.

FIG. 20 illustrates an example of an HEW-SIG-B structure in a case wherea channel is allocated subchannels not adjacent in a 40-MHz bandwidthaccording to the first embodiment. In the HEW-SIG-B structure of FIG. 20, channel allocation is possible for up to two reception apparatuses.FIG. 21 illustrates an example of an HEW-SIG-B structure in a case wherea channel is allocated subchannels not adjacent in an 80-MHz bandwidthaccording to the first embodiment. In the HEW-SIG-B structure of FIG. 21, channel allocation is possible for up to four reception apparatuses.

Illustrative structures of a BW field, an MCS field, a partial AIDfield, and an OFDMA pattern are in Table 6. Table 4 illustrates anexample of an HEW-SIG-B structure according to the present embodiment.

TABLE 6 Maximum Name number of bits Note OFDMA pattern 16 Allocationstructure in 20-MHz channel units used by each channel in OFDMA mode,using 4 bits for each channel Ex) Indicate 80 MHz in terms of positionin a bitmap format in 20-MHz unit When 20 MHz is allocated: 1000, 0100,0010, 0001 When 40 MHz is allocated: 1100, 1010, 1001, 0110, 0101, 0011When 80 MHz is allocated: 1111 MCS 16 Same as in Table 4 Partial AID 36Same as in Table 4

A reception apparatus may verify whether a PPDU operates in OFDMA basedon OFDMA bits of HEW-SIG-A and identify a space-time stream of eachchannel from OFDMA NSTS. Further, the reception apparatus may identify acoding mode of each channel from OFDMA coding. In the presentembodiment, unlike in the channel of the adjacent subchannels, awireless communication apparatus may indicate using a four-bit OFDMApattern, instead of a two-bit BW, that subchannels not adjacent areallocable. For example, when first and fourth channels among channels in20-MHz units are used, an OFDMA pattern mapped on [1001] may bereceived.

<HEW-SIG-B structure when allocation in 20-MHz or lower subchannel andsymbol unit is possible>

When a signal-to-interference-plus-noise ratio (SINR) or channelcharacteristics are identified by 20 MHz or lower, a subchannel unit maybe 20 MHz or lower and transmitting data using a channel with a goodSINR improves reception performance of a reception apparatus. Whensubchannels in 20 MHz or lower are allocated, various combinations forchannel configurations may be created and information on a channelconfiguration may be transmitted through bits of an OFDMA pattern ofHEW-SIG-B.

FIG. 22 is a diagram illustrating an example of an HEW-SIG-B structurein a case where allocation is performed by subchannel orsubchannel/symbol in a 40-MHz bandwidth according to the firstembodiment. Referring to FIG. 22 , the HEW-SIG-B structure illustratedin FIG. 22 may also be easily extended in an 80-MHz bandwidth or greateras in the relationships between FIGS. 18 and 19 . An OFDMA pattern has,for example, seven bits but may have smaller or greater bits than sevenbits.

FIGS. 23A and 23B are diagrams illustrating examples of dividing an80-MHz bandwidth into 10-MHz subchannels and symbols according to thefirst embodiment. FIG. 23A and FIG. 23B illustrate structures when abandwidth is 80 MHz and subchannels are allocable by 10 MHz. AlthoughFIG. 23A illustrates an example in which the same subchannel allocatedto a first symbol is allocable without any change depending on a symboland FIG. 23B illustrates an example in which an allocated subchannel mayvary depending on a symbol, a bandwidth may be configured variously.

A subchannel allocation mode may be configured with the example of FIG.23A, the example of FIG. 23B or in combination of these examples.Subchannel allocation information (subchannel allocation informationindicated by the bits of the OFDMA pattern) may be identified by atransmission apparatus and a reception apparatus in an informationexchange process upon initial connection. The reception apparatus mayidentify the subchannel allocation information from the bits of theOFDMA pattern upon transmission and reception of data.

Table 7 illustrates an example of allocation of subchannels and symbolsidentified from the OFMDA pattern in the present embodiment.

TABLE 7 Number of STAs involved in simultaneous Bandwidth OFDMAAllocated transmission (MHz) pattern subchannel (FIG. 23) 2 40 0010001{000, 010, 011, 111} 20 1010000 {110} 3 20 0110101 {010} 40 1000110{001, 100, 101, 111} 20 0101101 {000}

In the foregoing description, a channel is allocated by 20 MHz but isnot limited thereto.

Second Embodiment

FIG. 24 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a second embodiment, which is an example of an HEW-SIG-Astructure in a case where a short GI may be different by channel. As inrelationships between FIGS. 16 and 17 , bits and positions of compositenames in FIG. 24 may be modified variously.

FIG. 25 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the second embodiment, which is an example of an HEW-SIG-Bstructure in a 40-MHz bandwidth. Inserting a short GI into HEW-SIG-B foreach channel may extend the structure as in FIGS. 26 and 27 by adjustingreserved bits and bits for an OFDMA pattern of FIGS. 20 and 22 even whenthe OFDMA pattern is used instead of a BW. FIGS. 26 and 27 are diagramsillustrating other examples of an HEW-SIG-B structure according to thesecond embodiment. The HEW-SIG-B structures illustrated in FIGS. 25 to27 may be extended for a frequency band with a bandwidth of 80 MHz orgreater as in the relationships between FIGS. 18 and 19 .

Third Embodiment

FIG. 28 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a third embodiment, which is an example of an HEW-SIG-Astructure in a case where space-time block coding (STBC) may bedifferent by channel. As in the relationships between FIGS. 16 and 17 ,bits and positions of composite names in FIG. 24 may be modifiedvariously.

FIG. 29 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the third embodiment, which is an example of an HEW-SIG-Bstructure in a 40-MHz bandwidth. The HEW-SIG-B structure illustrated inFIG. 29 may be extended for a band with a bandwidth of 80 MHz or greateras in the relationships between FIGS. 18 and 19 . Further, insertingSTDB into HEW-SIG-B for each reception apparatus may extend thestructure by adjusting reserved bits and bits for an OFDMA pattern ofFIGS. 20 and 22 even when the OFDMA pattern is used instead of a BW.

Fourth Embodiment

FIG. 30 is a diagram illustrating a transmission process in a case whereOFDMA and MU-MIMO are combined according to a fourth embodiment.Referring to FIG. 30 , a bandwidth may be divided into a plurality ofchannels and each channel may be occupied by a plurality of stations,not a single station, so that MU-MIMO transmission by channel may beperformed.

An HEW-SIG-B generator 3010 may generate an HEW-SIG-B sequence includingdifferent pieces of information by channels. The HEW-SIG-B sequence maybe generated as many as a number of stations determined to be involvedin transmission by each channel. The generated HEW-SIG-B sequence may besubjected to a channel encoder 3015 and an interleaver 3020 and bemodulated by a constellation mapper 3025. The modulated sequence may besubjected to a CSD performer 3030 and be mapped on a beamforming matrixby a spatial mapper 3035.

A subchannel mapper 3040 may map the signal transmitted from the spatialmapper 3035 on a subchannel, and an IDFT performer 3045 may perform IDFTon the signal transmitted from the subchannel mapper 3040. A GI inserter3050 may insert a GI into the signal transmitted from the IDFT performer3045 and perform windowing on the signal. An RF communicator 3055 maytransmit the signal transmitted from the GI inserter 3050 through an RFantenna. HEW-SIG-B may be transmitted via beamforming, and a receptionapparatus is allowed to demodulate only a channel transmitted to thereception apparatus and thus may need to recognize the channeltransmitted to the reception apparatus through HEW-SIG-A.

FIG. 31 is a diagram illustrating an example of an HEW-SIG-A structureaccording to the fourth embodiment, which is an example of an HEW-SIG-Abit structure in a case where OFDMA and MU-MIMO (including beamforming)are combined. As in the relationships between FIGS. 16 and 17 , bits andpositions of composite names in FIG. 31 may be modified variously.

To indicate that transmission is performed by a combination of OFDMA andMU-MIMO, HEW-SIG-A may include bits indicating an OFDMA (B2 in FIG. 31 )and bits indicating a MU (B3 in FIG. 31 ). A reception apparatusoperating by MU-MIMO or beamforming is unable to demodulate a channelother than a channel selected for the reception apparatus and thus mayneed to recognize the channel selected for the reception apparatus.CH_SEL_ID may include information on a channel which each receptionapparatus needs to demodulate. An OFDMA pattern indicates a pattern of achange in a case where allocation changes by channels not adjacent orsymbol as in FIG. 23 .

FIG. 32 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the fourth embodiment, which is an example of an HEW-SIG-Bstructure when a channel indicated in CH_SEL_ID has a bandwidth of 20MHz. When the selected channel has bandwidths of 40 MHz and 80 MHz, thebandwidths may be easily extended by repeatedly transmitting 20 MHz asin FIG. 32 .

FIG. 33 is a diagram illustrating a reception mode according to thefourth embodiment. In FIG. 33 , it is assumed that a channel isconfigured by 20 MHz. Referring to FIG. 33 , a transmission apparatusconducts transmission to reception apparatuses connected to thetransmission apparatus by sequentially allocating higher transmissionbands, that is, allocating a 20-MHz channel to {6, 10}, a 40-MHz band to{1, 4, 7}, and 20 MHz to {9}.

A reception apparatus may identify a channel allocated to the receptionapparatus through CH_SEL ID of HEW-SIG-A. When subchannels not adjacentare used, the reception apparatus may identify a combination ofsubchannels allocated to a channel using an OFDMA pattern. When a CH_SELID value is a value to which the reception apparatus does not belong,which means that there is no allocated channel in a current PPDU, thereception apparatus terminates reception to save power consumption.

When a channel allocated to the reception apparatus is 40 MHz at amiddle position, the reception apparatus may perform demodulationthrough an HEW-STF of the channel and estimate a channel through anHEW-LTF to demodulate HEW-SIG-B. The reception apparatus may identify asubsequent preamble structure after NLTF or NSTS total based on ademodulation result and perform demodulation based on NSTS information.

Fifth Embodiment

FIG. 34 is a diagram illustrating an example of an HEW-SIG-A structureaccording to a fifth embodiment, which is an example of an HEW-SIG-Astructure in a case where HEW-SIG-B indicates an NSTS. As in therelationships between FIGS. 16 and 17 , bits and positions of compositenames in FIG. 24 may be modified variously.

FIG. 35 is a diagram illustrating an example of an HEW-SIG-B structureaccording to the fifth embodiment, which is an example of an HEW-SIG-Bstructure in a 40-MHz bandwidth. The HEW-SIG-B structure illustrated inFIG. 35 may be extended for a bandwidth of 80 MHz or greater as in therelationships between FIGS. 18 and 19 . The structure may be easilyextended from the embodiment of FIG. 35 by adjusting reserved bits andbits for an OFDMA pattern of FIGS. 20 and 22 even when the OFDMA patternis used instead of a HEW-SIG-B BW for each channel.

FIG. 36 is a flowchart illustrating operations of a wirelesscommunication method according to an embodiment. The wirelesscommunication method may be performed by a wireless communicationapparatus including at least one processor. Referring to FIG. 36 , thewireless communication apparatus may generate an HEW frame including atleast one of an HEW-SIG-A field and an HEW-SIG-B field which includechannel information for communication according to an OFDMA mode inoperation 3610.

According to one embodiment, the HEW-SIG-A field may include at leastone of bit information indicating an OFDMA mode, bit informationindicating a number of space-time streams (NSTS) of channels transmittedin the OFDMA mode, and bit information indicating a coding mode ofchannels transmitted in the OFDMA mode.

According to another embodiment, the HEW-SIG-A field may include atleast one of bit information indicating an OFDMA mode, bit informationindicating an MU-MIMO mode, and bit information indicating a channel tobe demodulated by each reception apparatus.

The HEW-SIG-B field may include at least one of bit informationindicating a bandwidth used by each channel in the OFDMA mode, bitinformation indicating a modulation and coding mode used by each channelin the OFDMA mode, bit information indicating a partial AID used by eachchannel in the OFDMA mode, bit information including subchannelallocation information in the OFDMA mode, and bit information indicatinga number of space-time streams (NSTS) of channels transmitted in theOFDMA mode. The bit information indicating the subchannel allocationinformation in the OFDMA mode may indicate channel allocationinformation in a bitmap format in a 20-MHz frequency bandwidth unit.According to one embodiment, the subchannel allocation information inthe OFDMA mode may include allocation information on subchannels notadjacent or information on a subchannel allocated in a frequencybandwidth unit greater than 0 and smaller than 20 MHz.

The wireless communication apparatus may transmit the generated HEWframe to at least one reception apparatus in operation 3620. Accordingto one embodiment, the wireless communication apparatus may transmit theHEW-SIG-B field using a frequency bandwidth indicated in the HEW-SIG-Afield.

FIG. 37 is a flowchart illustrating operations of a wirelesscommunication method according to another embodiment. The wirelesscommunication method may be performed by a wireless communicationapparatus including at least one processor. Referring to FIG. 37 , thewireless communication apparatus may receive, from a transmissionapparatus, an HEW frame including at least one of an HEW-SIG-Afield andan HEW-SIG-B field which include channel information for communicationaccording to an OFDMA mode in operation 3710.

The wireless communication apparatus may determine a channel to be usedfor communications using the channel information included in at leastone of the HEW-SIG-A field and the HEW-SIG-B field included in thereceived HEW frame in operation 3720. According to one embodiment, thewireless communication apparatus may determine, based on the channelinformation included in the HEW-SIG-A field, a channel through which theHEW-SIG-B field is transmitted. The wireless communication apparatus maydemodulate the HEW-SIG-B field based on an HEW-LTF included in theHEW-SIG-A field.

In the present invention, data is simultaneously transmitted to aplurality of stations using a 20-MHz unit or lower unit, therebyincreasing frequency utilization efficiency.

The methods according to the embodiments may be realized as programinstructions implemented by various computers and be recorded innon-transitory computer-readable media. The media may also include,alone or in combination with the program instructions, data files, datastructures, and the like. The program instructions recorded in the mediamay be designed and configured specially for the embodiments or be knownand available to those skilled in computer software. Examples of thenon-transitory computer readable recording medium may include magneticmedia such as hard disks, floppy disks, and magnetic tape; optical mediasuch as CD ROM disks and DVDs; magneto-optical media such as flopticaldisks; and hardware devices that are specially configured to store andperform program instructions, such as read-only memory (ROM), randomaccess memory (RAM), flash memory, and the like. Examples of programinstructions include both machine codes, such as produced by a compiler,and higher level language codes that may be executed by the computerusing an interpreter. The described hardware devices may be configuredto act as one or more software modules in order to perform theoperations of the above-described exemplary embodiments, or vice versa.

While a few exemplary embodiments have been shown and described withreference to the accompanying drawings, it will be apparent to thoseskilled in the art that various modifications and variations can be madefrom the foregoing descriptions. For example, adequate effects may beachieved even if the foregoing processes and methods are carried out indifferent order than described above, and/or the aforementionedelements, such as systems, structures, devices, or circuits are combinedor coupled in different forms and modes than as described above or besubstituted or switched with other components or equivalents.

Thus, other implementations, alternative embodiments and equivalents tothe claimed subject matter are construed as being within the appendedclaims.

1. Wireless communication method performed by a wireless communicationapparatus in a wireless local area network (WLAN) system, the wirelesscommunication method comprising: generating a frame comprising an SIG-Afield and an SIG-B field, wherein the SIG-B field comprises bitinformation that comprises subchannel allocation information in anOrthogonal Frequency-Division Multiple Access (OFDMA) mode wheredifferent subchannels are allocated to different users and simultaneousdata transmission to multiple users is allowed; and transmitting thegenerated frame to the multiple users, wherein the transmitting of theframe transmits the SIG-B field using a frequency bandwidth indicated inthe SIG-A field, and wherein each of the subchannels represents aminimum allocation unit.
 2. The wireless communication method of claim1, wherein the bit information further indicates at least one of apartial allocation identifier (AID) used by each channel in the OFDMAmode, a modulation and coding mode used by each channel in the OFDMAmode and a number of space-time streams (NSTS) of channels transmittedin the OFDMA mode.
 3. The wireless communication method of claim 1,wherein the subchannel allocation information indicates a position ofeach of subchannels in a channel bandwidth of 20 MHz, 40 MHz, 80 MHz, 80MHz+80 MHz, or 160 MHz in the OFDMA mode, and wherein a frequencybandwidth of each of the subchannels is greater than 0 and smaller than20 MHz.
 4. The wireless communication method of claim 1, wherein thefrequency bandwidth of each of the subchannels is dynamically set from 0to 20 MHz.
 5. A wireless communication method performed by a wirelesscommunication apparatus in a wireless local area network (WLAN) system,the wireless communication method comprising: receiving, by the wirelesscommunication apparatus corresponding to one of multiple users from atransmission apparatus, a frame comprising an SIG-A field and an SIG-Bfield, wherein the SIG-B field comprises bit information that comprisessubchannel allocation information in an Orthogonal Frequency-DivisionMultiple Access (OFDMA) mode where different subchannels are allocatedto different users and simultaneous data transmission to the multipleusers is allowed; and determining each of subchannels to be used forcommunications based on at least the subchannel allocation information,wherein the transmitting of the frame transmits the SIG-B field using afrequency bandwidth indicated in the SIG-A field, and wherein each ofthe subchannels represents a minimum allocation unit.
 6. The wirelesscommunication method of claim 5, wherein the bit information furtherindicates at least one of a partial allocation identifier (AID) used byeach channel in the OFDMA mode, a modulation and coding mode used byeach channel in the OFDMA mode and a number of space-time streams (NSTS)of channels transmitted in the OFDMA mode.
 7. The wireless communicationmethod of claim 5, wherein the subchannel allocation informationindicates a position of each of subchannels in a channel bandwidth of 20MHz, 40 MHz, 80 MHz, 80 MHz+80 MHz, or 160 MHz in the OFDMA mode, andwherein a frequency bandwidth of each of the subchannels is greater than0 and smaller than 20 MHz.
 8. The wireless communication method of claim5, wherein the frequency bandwidth of each of the subchannels isdynamically set from 0 to 20 MHz.
 9. The wireless communication methodof claim 5, wherein the wireless communication apparatus demodulates theSIG-B field based on an LTF comprised in the SIG-A field.
 10. A wirelesscommunication apparatus comprising: a processor to generate a framecomprising an SIG-A field and an SIG-B field, wherein the SIG-B fieldcomprises bit information comprising subchannel allocation informationin an Orthogonal Frequency-Division Multiple Access (OFDMA) mode wheredifferent subchannels are allocated to different users and simultaneousdata transmission to multiple users is allowed; and a transmitter totransmit the generated frame to the multiple users, wherein thetransmitting of the frame transmits the SIG-B field using a frequencybandwidth indicated in the SIG-A field, and wherein each of thesubchannels represents a minimum allocation unit.